Poly(arylene sulfide ketone), henceforth abbreviated as PASK, and poly(arylene sulfide diketone), henceforth abbreviated as PASDK, resins are engineering thermoplastics of potential commercial interest for film, fiber, molding, and/or composite applications because of their outstanding thermal and mechanical properties. General processes for the production of PASK and PASDK are known in the art. For example, PASK and PASDK can be prepared by the reaction of an alkali metal sulfide in a polar organic compound with a polyhaloaromatic ketone or a polyhaloaromatic diketone, respectively.
Disadvantages often associated with the production of PASK and PASDK resins pertain to the recovery and handling of the polymer produced. Specifically, at the completion of a typical polymerization reaction, the reaction mixture is generally in the form of a slurry comprising a liquid phase (e.g., predominantly a polar organic compound and water) and a particulate phase (e.g., predominantly polymeric resin and by-product salts), wherein the polymeric resin when recovered is in the form of powder-like particles. These powder-like particles generally have bulk densities of less than about 10 lbs/ft.sup.3 when recovered. The slurry containing this extremely fine powder-like resin filters very slowly and, thus, hampers the polymer's washability, recoverability and processability. Washing, recovering and/or processing PASK and PASDK resins, which have low bulk densities, are extremely difficult.
While a technique which increases the resin's bulk density could be advantageous to the commercial industry by improving the resin's handling, there are, however, some applications where such a technique would not be the most preferred mode for improving handling procedures. Specifically, in some commercial applications, it is necessary to have the PASK or PASDK resin in the form of a fine powder. Examples of such commercial applications include, but are not limited to, powder coating, slurry coating and some types of compounding operations.
If a technique were employed which improved handling procedures by increasing the bulk density of the PASK or PASDK resins, and if these resins were to be employed in a process requiring the polymer to be in the form of a powder, the resulting resin might have to be milled or ground. Therefore, in those applications wherein it is desirable to use PASK or PASDK resins while in a powder form, it would be advantageous to improve the handling of the respective resins while not increasing their bulk densities.
A PASK or PASDK resin should be relatively free from metal halide salts and other ash-producing contaminants to be of full usefulness and value. Another problem in the production of PASK and PASDK resins has been the separation of high purity polymer from the contaminants in its polymerization reaction slurry. The polar organic compounds generally used in polymerization processes often cause difficulty in separating the polymer from its reaction mixture slurry by such usual means as filtration since the liquid component and the polymer often produce a filter cake of such "pasty" physical characteristics that plugging of the filter is a continuous problem and washing the filter cake free of other contaminants is difficult.
To avoid these problems, methods have been proposed for removal of the non-polymeric liquid component from the polymer slurry before separation of the polymer and other contaminants is attempted. One such method is the rapid, reduced-pressure evaporation of the non-polymeric liquid component, often called a "flash-recovery" process. Generally, in a flash-recovery process, the polymerization mixture comprising the polymer product, a polar organic compound and water, is at a superatmospheric pressure and at a temperature which is greater than the atmospheric boiling points of most non-polymeric liquids present therein. This polymerization mixture is then transported across a "flash valve". This rapidly reduces the pressure exerted on the mixture and results in the vaporization of essentially all non-polymeric liquids contained therein while simultaneously solidifying the polymeric liquids in the form of a particulate resin.